Anti-infective properties of vitamin A.

1. Six months after feeding a vitamin A free diet the liver content of mice was markedly reduced but not yet completely exhausted. These vitamin A deprived mice were either immunized with sheep erythrocytes or infected with Listeria monocytogenes. In comparison to normal control mice no significant difference ws observed. This indicates that neither the immune system nor the mononuclear-phagocytic system was involved. 2. Mice treated with a high dose of vitamin A showed increased antibody production against sheep erythrocytes and also increased resistance against infection with L. monocytogenes. These experimental findings indicate a stimulatory effect on the immune system and the mononuclear phagocytic system. As a conclusion it is deduced that the term "anti-infective vitamin" does not hold absolutely true for vitamin A, although certain anti-infective properties cannot be denied.